Centrifugal compressor



Jan. 7, 1941. BlRKlGT 2,228,194

CENTRIF-UGAL COMPRESSOR Filed Aug. 16, 1959 2 Sheets-Sheet 1 In yen-tor:

Jan; 7, 1941. BIRKIGT CENTRIFUGAL COMPRESSOR Fil ed Aug. 16, 1939 2 Sheets-Sheet 2 .Tnveniar:

Patented Jan. 7, 1941 I i UNITED STATES PATENT OFFICE 4 1' Louis Birkigt, Versoix, near Geneva, Switzerland Application August 16, 1939, Serial No. 290,465 In Belgium May 17, 1939 Claims. (Cl. 230-127) This invention relates to centrifugal air and other elements, a rotor I provided with a plulike compressors having at least one blade wheel rality of blades or vanes 2 adapted, when the said or the like, compressing, by centrifugal effect, the rotor is rotated, to distribute,by centrifugal effect, air or other gaseous fluid between co-operating air or other gaseous fluid between fixed blades 3 5 fixed blades which latter canalise the compressed regularly distributed on a stator 4 and set in such 5 fluid towards a discharge outlet, the said fixed a manner as to canaiise the fluid coming from the blades generally being profiled and in each lonrotor I towards a discharge manifold 5. gitudinal section having a median line, and Regarding this mechanism as a whole, with the concerns more particularly but not exclusively, exception of the fixed blades 3 comprised therelO amongst such compressors, those for internal by, it can be constructed in any suitable usual combustion engines, particularly such engines for manner .and especially, as shown, so that the aircraft, and has for its main vobject not only to blades or vanes 2 of its rotor are formed by plane increase the efliciency of such compressors genelements arranged radially. erally but to evolve such devices in which the It has been ascertained, experimentally, with gaseous fluid dealt with is heated to a lesser such a mechanism the streams of air or other 5 extent than hitherto. gaseous fluid leave the trailing edge AB of each The present invention takes account of the fact blade or vane 2 in a direction (which is the rethat in compressors oi.the kind concerned, the sultant' of a radial component and of a tangenstreams of gaseous fluid leave the blades of the tial component) forming with the plane of this 2 rotor in directions the line of which varies along blade or vans an angle the value of which is vari- 20. the trailing edge of each of the rotor blades, and able along the said'trailing edge. In particular, generally in accordance with, the invention the in the neighbourhood of the middle region of the fixed co-operating blades are given such a form trailing edge AB, the said. angle has a lower value that the streams of fiuid leaving the rotor attack than towards the extremities of the said trailing the various longitudinal sections of each such edge. a

fixed blade substantially according to the tan- The method of investigation which will be more gents to the part of the respective median lines explicitly mentioned hereafter established that of the said sections which come at or towards the extreme values of the angle in question can the leading edge of the said blade. have a variation of the-order of 10, this varia- In addition, and preferably, such fixed blades tion being all the more considerable as the dis- 30 have transverse sections in planes at right angles tance from the rotor is greater. g to their longitudinal sections, which are curved By way of example, there has been shown (Fig. andthe curvature of which increases from the 7) an experimental diagram of the variations of leading edge thereof (where it is preferably the said angle along the trailing edge AB. This 5 straight) towards the rear trailing edge. curve is generally found to be asymmetric from In order that the invention may be better unthe fact particularly that, towards the extremity derstood, it will now be described with reference A of the said trailing ed e e s 0 air are to the accompanying drawings, which are given subjected to the action of the wall of the rotor by way of exam-pie only and in which: whereas towards the extremity B they are braked 40 Fig. 1 shows, part in elevation, part in secby thev wall of the stator. 40 tion, a compressor constructed according to the Now. it is of advantage, insuch'a compressor, invention. to reduce to the minimum the aerodynamic brak Flg. 2 is a section along the line II--II, Fig. 1. ing produced by the fixed blades 3 to lmprove the Fig. 3 shows, on.a larger scale and in section, efllciency of the system as a whole.

5 a detail of Fig. 1. For this purpose and to avoid the defect in Flgs. 4 to 6 are sections respectively along the such compressors as hitherto known. that some lines IV-IV, V--V and VIVI, Fig. 3; of the streams coming from-the blades or vanes Fig. 7 is a diagram to facilitate the understand- I are ot o re tly uided by t e ixed blades 3, ing of the invention, and v the form of the said blades 3, according to the Fig. 8 is a diagram illustrating a method of principal arrangement of the invention, is adapt- 5O investigation for the study of gaseous currents or ed to that of the gaseous stream issuing from the pressures in the interior of the compressor. --trailing edge AB of each blade or vane 2.

The drawings show a compressor for air or In other words, the blades 3 are given such a other gaseous fl-uid suitable for charging (for exform that the streams of fluid distributed in difample) an aircraft engine and comprises, among ferent directions by the aforesaid trailing edge 55 casing of the compressor but without fixed blades attack the various longitudinal sections of the fixed blades 3 according to the tangents to the parts of the respective median lines of the said sections which come at or towards the leading edge of the said fixed blades. For this purpose and for example, the embodiment illustrated by the drawings may be adopted, according to which a certain curvature is given to the median lines of each blade 3 (which curvature is variable from one median line to the other) the concavity of the said blade being, for example, turned towards the exterior, so that the said blade is given, in the general direction. of its median lines, a somewhat streamlined shape similar in some respects to that given to the wings of aircraft, each median line being so directed as to be attacked tangentially by the streams of air opposite which it will come when in working position.

Further, the arrangement is such that the transverse sections of this blade, such as shown particularly by Fig. 5 and Fig. 6, are of curved shape and present an increasing curvature proceeding towards the trailing edge of the blade, the leading edge preferably being of substantially rectilinear shape as shown by Fig. 4.

It should be observed that these transverse sections, the shape of which is derived from the diagram of Fig. '7, will be generally asymmetric in a similar manner to the said diagram.

It is seen, from the foregoing, that it is necessary to take into account, for constructing the fixed blades 3, the direction according to which the gaseous fluid leaves each of the points of the trailing edge of the blades or vanes 2.

For determining these directions, any appropriate testingmethod may be adopted, particularly that more explicitly mentioned hereafter (by way of example).

According to this method, which is illustrated diagrammatically by Fig. 8 of the drawings, after having placed the rotor I provided with its blades or vanes 2 in its conditions of use and particularly having mounted it in a casing similar to the 3, there is brought successively opposite the trajectory of each of the points of the trailing edge AB of the blade or vane 2 (in the region where the leading edge of a fixed blade 3 will be located) a pressure gauge 6 branched on a manometer l, the said gauge being formed, for example, by a hollow tube in the extremity of which is disposed a lateral aperture 8 the axis of which is perpendicular to that of the said tube.

For each axial position of the gauge 6. it is rotated around its axis to determine the setting of the orifice 8 for which the pressure is maximum, this setting defining the theoretical direction of the streams of fluid under pressure at the point concerned of the trailing edge AB.

By repeating this operation all along the said trailing edge, it will be possible to ascertain a large number of theoretical directions of the streams of fluid and, in consequence, to deter mine, with precision, the form to given to the I fixed blades 3.

By this method of investigation it will also be possible to determine, for each point of the trailing edge AB, the absolute value of the speed of the gaseous'stream issuing from the said point.

The operation of the compressor constructed as described will be well understood without further description; it presents the advantage of having an efficiency superior to such compressors their trailing edges towards the periphery thereof,

inlet means for gaseous fluid in the casing leading to the rotor, outlet means from the casing for the gaseous fluid leaving the rotor around the periphery of the rotor, and a plurality of spaced fixed guiding blades for the gaseous fluid leaving the rotor, extending from side to side of the casing adjacent to and having their median lines intersecting at the leading edges of the guiding blades with radii of the rotor, to lead the issuing gaseous fluid therebetween to the outlet means, the median lines of the longitudinal sections in the fixed guiding blades adjacent the leading edges thereof having from side to side slightly variable angular positions in relation to the periphery of the rotor, the tangent to the median line at any longitudinal section adjacent said front edge lying in the line along which the gas streams strike the leading edges of the fixed guiding blades in the same longitudinal plane.

2. A centrifugal compressor for gaseous fluids of the type comprising a casing, a rotor mounted to turn in such casing, a plurality of impeller blades angularly spaced and carried by such rotor with their trailing edges towards the periphery thereof, inlet means for gaseous fluid in the casing leading to the rotor, outlet means from the casing for the gaseous fluid leaving the rotor around the periphery of the rotor, and a plurality of spaced fixed guiding blades of streamline shape inlongitudinal section for the gaseous fluid leaving the rotor, extending from side to side of the casing adjacent to and having their median lines intersecting at the leading edges of the guiding blades with radii of .the rotor, to lead the issuing gaseous fluid therebetween to the outlet means, the median lines of the longitudinal sections in the fixed guiding blades adjacent the leading edges thereof having from side to side slightly variable angular positions in relation to the periphery of the rotor, the tangent to the median line at any longitudinal section adjacent said front edge lying in the line along which the gas streams strike the leading edges of the fixed guiding blades in the same longitudinal plane.

3. A centrifugal compressor for gaseous fluids as claimed in claim 1 in which each fixed guiding blade from one side of the casing to the other side has a variable transverse cross section which at the leading edge is substantially straight and which is of increasing curvature proceeding towards its trailing edge. I

4. A centrifugal compressor for gaseous fluids as claimed in claim 1 in which each fixed guiding blade from one side of the casing to the other .70 at the leading edge is substantially straight and side has a variable transverse cross section which compressor for gaseous fluids as claimed in claim 1 in which each fixed guiding 1 blade from one side of the casing to the other side has a variable transverse cross'section which at theleading edge is substantially straight and which is of increasing curvature towards the trailing edge, the curvature of the trailing edge being asymmetric from side to side and corresponding with the diflerent directions in which the streams of gaseous fluid strike the individual points of the 1eadihg;\edges of the fixed guiding blades. LOUIS BIRKIGT. 

